On Tue, 5 Oct 2004 12:26:06 -0500, "John Smith"
wrote:

You should get 1.0 @ 180° (the definition of a short).

Well, that's not possible when feeding a length of RG58 at 400 MHz, is it?
Remember, I said that there was about a 5 foot length of RG58 between the
directional coupler and the load. How can one get 1.0 reflected to the
coupler when the load is a short? That requires zero loss coax.

Hi John,

As Wes suggests, butt up the load against the directional coupler
output and eliminate this arbitrary loss of the 5 foot RG58. It
should also shift the readings too (you are simply walking around the
circle of constant SWR). One question that would be obviated in this
process (but I have to ask anyway) is WHERE was this short you
applied? At the output port of the coupler, or at the end of this 5
foot RG58? (Same question applies to the calibrated load).

The other measurements that you reported in response to Wes indicate
you have tracking ports (even if they are off by 4dB). As I said, it
seemed unlikely this would be a problem and it confirms the
out-of-octave specification.

73's
Richard Clark, KB7QHC

"Richard Clark" wrote in message
news
On Tue, 5 Oct 2004 12:26:06 -0500, "John Smith"
wrote:

You should get 1.0 @ 180° (the definition of a short).

Well, that's not possible when feeding a length of RG58 at 400 MHz, is it?
Remember, I said that there was about a 5 foot length of RG58 between the
directional coupler and the load. How can one get 1.0 reflected to the
coupler when the load is a short? That requires zero loss coax.

Hi John,

As Wes suggests, butt up the load against the directional coupler
output and eliminate this arbitrary loss of the 5 foot RG58. It
should also shift the readings too (you are simply walking around the
circle of constant SWR). One question that would be obviated in this
process (but I have to ask anyway) is WHERE was this short you
applied? At the output port of the coupler, or at the end of this 5
foot RG58? (Same question applies to the calibrated load).


I used a 66 inch piece of RG58 between the directional coupler and the load.
It was at the load end of this piece of coax that I calibrated with a short
and made the load measurements.


The other measurements that you reported in response to Wes indicate
you have tracking ports (even if they are off by 4dB). As I said, it
seemed unlikely this would be a problem and it confirms the
out-of-octave specification.

73's
Richard Clark, KB7QHC